Credit: The Associated Press

New York Yankees' CC Sabathia delivers a pitch against the Houston Astros in the first inning of a baseball game on opening day for the teams, Tuesday, April 1, 2014, in Houston. (AP Photo/Pat Sullivan)

HOUSTON — It’s one of baseball’s oldest axioms, the one that insists the real season doesn’t begin until opening day’s frills are out of the way. It’s all about ceremony and symbolism when the curtain goes up, the official end of winter and the resurrecting of the boys of summer.

So why was CC Sabathia’s performance against the Astros on Tuesday so painful for Yankees fans to watch, and so unsettling to an organization that wants to believe its ace can flourish with diminished stuff?

Say what you want about the way Sabathia settled down over his last four innings, holding the Astros scoreless – it was all for cosmetic effect. Truth was, the big left-hander put the Bombers in an insurmountable hole, pitched them right out of the game by allowing six runs in the first two innings. The Astros sent 13 men to the plate in the early carnage, en route to a 6-2 victory over the Yankees’ team that gorged itself on a $438 million stimulus package this winter.

Time will tell, of course, whether Joe Girardi’s offense will be more dangerous than it was against starter Scott Feldman, who didn’t allow a run and surrendered just two hits for 6 2/3 innings. The more important question is whether Sabathia is any different or any better than he was in 2013, when his 4.78 ERA and 28 HRs represented career worsts.

Sabathia showed up in spring training promising to be smarter, more efficient and more streamlined with his fastball, even if it no longer reached 90 mph. And for most of March, the left-hander was as good as advertised, even finishing out the Grapefruit League action with 16 consecutive scoreless innings. This was the new Sabathia, alright, as mellow as a 40’s-era jazz musician, complete with an Eastern philosophy about getting hitters out.

So it was reasonable to believe the Yankees would roll right over the Astros on Opening Day. Talk about the ultimate therapy session: these were the same Astros who finished last in the American League in OPS in 2013 and concluded the season with a stunning 15-game losing streak. The Astros weren’t just bad, they were hopeless.

Even a former star pitcher in decline, like Sabathia, should’ve had his way with this Class AAA lineup – even with a subpar history on Opening Day assignments (5.80 ERA in 11 starts). Except that Sabathia ran straight into a revelation the moment he took the mound: the Astros didn’t fear him. The man who used to intimidate hitters with a 96-mph fastball delivered on a downhill trajectory – pure poison to anyone standing 60 feet, six inches away – suddenly had nothing to make hitters uncomfortable.

You knew Sabathia was in trouble the moment leadoff hitter Dexter Fowler blasted a monster double over Jacoby Ellsbury’s head, all the way to Tal’s Hill some 400 feet away in straight-away center.

Robbie Grossman’s fly ball to right put Fowler on third, and two pitches later, Jose Altuve’s sharp single to left gave the Astros the lead they’d never relinquish. The Yankees, meanwhile, plunged right into the cesspool, committing two errors over the span of the six-run outburst, and that didn’t even include Mark Teixeira’s errant throw past Brian McCann that allowed the Astros their second run.

It was an abysmal, if not embarrassing performance, but poor defense aside, it was Sabathia who made the Yankees’ hierarchy squirm. He gave up home runs in the first and second innings, both on 89-mph fastballs that simply didn’t have the precision or movement to give his 84-mph change-up an illusory quality.

The velocity-gap between the two pitches is too small for Sabathia to be this careless with his location. That’s another way of saying it’s going to a long summer unless Sabathia figures out how to avoid mistakes up in the strike zone.

Not surprisingly, Sabathia and Joe Girardi tried to put a positive spin on the numbers. The manager said he was “pleased” that Sabathia’s final 12 outs were so uneventful – the Astros produced just two singles – and that the ace “seemed to calm down and let it fly” once he finally got over the shock of the ambush.

Sabathia all but repeated Girardi’s explanation, saying he was “too amped up” from Opening Day jitters. They spoke in unison about the marathon ahead, that over the course of 162 games, games like this are bound to happen.

No one argues the point. It’s what every losing manager (and pitcher) says after getting beat on Day 1. But Sabathia’s back-story goes deeper than that. It’s about assuring the Yankees that he can beat the league’s best lineups, and not find himself gasping for air against the American League’s weaklings. If Sabathia can’t control bat-speed against the Astros, what’s going to happen the first time he runs into the Red Sox, or has to hold the Rays to one or two runs because they have the best pitching in the division, if not the AL?

That’s why Sabathia matters; that’s why the Yankees needed him to nuke the Astros right out of Minute Maid Park on Tuesday. If he couldn’t get them to swing and miss they he used to in his younger, more fearsome days, then Sabathia was supposed to finesses his way to a miniature classic, the way Andy Pettitte used to with virtually the same 89-mph.

Girardi’s rhetoric sounded an awful like propaganda when he said, “one of the things I worry about is the first start by a starting pitcher.” As if Sabathia had never taken the ball on Opening Day. But the manager was more truthful when he admitted, “this isn’t what I expected.”

No one did, least of all Sabathia, who, likewise spoke for the Yankee family when he finally stopped and surveyed the damage. “It just snowballed,” he said quickly. “Everything happened really quick.”